1. Field of the Invention
The present invention relates to a process for purifying an ethylene compound having a fluorine-containing organic group, and more particularly to a purification process by which iodine contained as impurity an ethylene compound having a fluorine-containing organic group can be removed effectively.
2. Description of the Prior Art
Ethylene compounds having a mono or bifuncitonal fluorine-substituted ethylenically unsaturated compound (hereinafter referred to as "fluorine-containing ethylene compounds") are capable of reaction with organosilicon compounds having Si-H bonds such as hydrosilane or hydrosiloxane (hydrosilylation reaction) in the presence of a platinum catalyst. Therefore, the fluorine-containing ethylene compounds are useful as compounds for introducing a fluorine-containing organic group into silane compounds, polysiloxanes, etc.
Such fluorine-containing ethylene compounds are, in general, synthesized according to the following reaction path: ##STR1## wherein Rf is a fluorine-containing organic group.
As is seen from the above reaction path, the fluorine-containing ethylene compounds contain iodides such as the starting material Rf-I and intermediate product. Rf-CH.sub.2 CH.sub.2 -I, as impurities. Where such a fluorine-containing ethylene compound is served to the aforementioned hydrosilylation reaction, the iodides contained as impurities in the ethylene compound generate molecular iodine during the reaction, and the molecular iodine acts as a catalyst poison. Consequently, the yield of the product obtained by the hydrosilylation reaction is low, and the product is colored in red due to the molecular iodine.
As a method of purifying the fluorine-containing ethylene compounds, there have been known a number of processes, for example, a process in which activated carbon is used to remove the impurities through adsorption, and a process in which a reducing agent is used to remove the impurities through reduction. These conventional processes are effective for removal of molecular iodine from the fluorine-containing ethylene compound, but are not effective in removing the iodides which are generation sources of the molecular iodine. Therefore, even where a fluorine-containing ethylene compound is served to the aforesaid hyirosilylation reaction after treated by such conventional purification process, the problems of yield and coloring of the product still remain unsolved.